Alter highlights how there may not be as much of a difference as one might think between the addictive potential of substances and behaviours. He talks about how, for instance, many apps such as Facebook and Instagram, are perfectly engineered to keep user hooked. I never quite realised the power of variable rewards - the dopamine hit of these often outweigh that of predictable rewards. While research on behavioural addictions is not as substantial as that on substance addictions, it is nonetheless something that cannot be neglected. The end of the book did not cohere very well for me, e.g. chapter on Gamification. Seemed a list of ideas, but doesn't seem to conclude satisfactorily. Still, this book is worthwhile in its dive into we can and are being manipulated in ways that may not be healthy for us.